To allow for improved ease of use, beverage containers may comprise resealable closures that can be operated without the need to unscrew or otherwise remove a cap, thereby allowing for one-handed operation. Conventional resealable closures comprising such features may have a valve that is operable by pulling or pushing on a portion of the closure, thereby allowing liquid contained in the bottle to flow out. The valve may either remain in an open configuration after being opened, allowing for continued flow of liquid as required, or may be configured to return to a closed configuration thereby resealing the container.
Such closures are typically mass manufactured via polymer injection moulding, using multi-cavity moulds configured to form the various components that are required to operate together to form the closures. In certain types of closures, for example where an automatically resealable valve is required, it can be difficult to achieve sufficiently small manufacturing tolerances to give the resulting product a uniform functionality regardless of the specific cavity each part is moulded in.
Various technical aspects are influenced by the way in which a resealable valve is configured. The drinking experience is strongly influenced by the ease of response of the closure valve, i.e. a more easily opened valve tends to result in an improved drinking experience. The valve should therefore be easy to operate, but should ideally not remain open, as this can result in leakage of the contents. However, return of air back into the bottle after drinking is an important concern to avoid deformation of the bottle, since the valve will ideally be air tight once it re-closes. Air returning to the bottle after drinking should therefore be controlled by configuration of the valve. A bottle closure having a configurable resealable valve that aims to address these issues is disclosed in published patent application US 2009/0212061. Configuring the closure such that a lower force tends to return the valve to its closed position allows for control over the timing of this venting function.
A competing requirement, however, is that the membrane should also be resistant to damage by biting or chewing, given that the valve will tend to be operated by mouth action alone. Since users may be children, a particularly important requirement is that any small components in the closure that may represent a choking hazard are not at risk of being separated during normal use. Typical requirements involve a resistance to loosening or breaking when a force of up to 60 N is applied. Furthermore, any detached part should not be so small that it could become lodged in the throat of the user. The British Soft Drinks Association has developed standards based on such requirements.
The aforementioned publication US 2009/0212061 discloses a pressure activated closure device for a beverage container, in which a pressure-sealing membrane is connected between an outer portion of the closure device and a centrally located drinking orifice portion. Movement of the drinking orifice portion results in flexure of the membrane and opening of a valve, allowing the liquid contents of the bottle to flow through the drinking orifice. The elasticity of the membrane ensures that the valve returns to its pressure-sealing position when an under-pressure supplied during drinking ceases. The deformable area of the membrane element must, due to its ring-formed shape, be either very thin or have a long extent in order to provide a sufficiently high flexibility for the membrane to be practically useful. This is an inherent weakness of the type of design in which membrane flexure occurs as a result of an extensive geometrical deformation in an area that by necessity is restricted to a small diametrical extent, i.e. the width of a bottle opening. Furthermore, in one embodiment the membrane is in its periphery only loosely connected to the remaining structure of the closure by means of a snap lock. This connection method provides the membrane with an increased freedom of movement in its outer portion, but this makes it difficult to design a sufficiently strong closure so that the above mentioned regulatory requirement for tensile strength is satisfied. To address this it may be necessary to use several types of plastic materials for the membrane, for example by using a stiffer material for the snap lock zone in relation to the deformation zone. This would result in a technically more complicated solution and as a result lead to the need to use a more expensive manufacturing process.
It is an object of the invention to address one or more of the above mentioned problems.